Sphaerophysa salsula is a species of flowering plant in the legume family known by the common names alkali swainsonpea, Austrian peaweed, and red bladder-vetch. It is native to Asia but it is known in many other parts of the world as an introduced species and often a noxious weed. It grows in cultivated land and disturbed habitat, easily tolerating alkaline substrates. It is commonly seen in areas where alfalfa is grown, because the seeds of the two species look similar and the weed seed is easily imported with the crop seed.